Determination of Total Salt Content in Relation to Electrical Conductivity of Slightly Saline Soils.

The study objective was to determine the relationship between total soluble cation concentration (TSC) and electrical conductivity (EC) of slightly saline soils (soils with an EC close to or above 4 decisiemens/meter at 25^o Celsius). Original research done on irrigated landscapes in California has shown that EC*10 is fairly equivalent to [Ca²⁺]+[Mg²⁺]+[Na⁺]; however, that relationship does not hold true in the Northern Great Plains area. Soil samples were collected in 2011 from two fields at footslope and summit landscape positions over two depths, 0-7.5 and 7.5-15 centimeters. Field locations were the North Central South Dakota Glacial Lake Basin (45.377614, -97.965533) and Northwestern South Dakota Missouri Plateau (45.377614, -100.825254). Saturated paste extraction method was completed on 100 gram samples and EC and TSC were measured. Preliminary data analysis reports a linear relationship between TSC and EC where "EC*8.12 = Ʃ([Ca²⁺]+[Mg²⁺]+[Na⁺]), R² = 0.603." The linear equation did not significantly vary between summit and footslope positions. For slightly saline soils in the Northern Great Plains, these research conclusions suggest that the EC / TSC relationship differs between dryland Northern Great Plains soils and irrigated agricultural landscapes in California.  The differences may be attributed to different salt sources.  In the Northern Great Plains regions, indigenous salts from lower soil horizons are brought to the surface due to high water tables. In California, soil salts originate from salty irrigation waters.